A radio access network (RAN) configuration has been changed such that various types of small cells such as a pico cell, a femto cell, etc. interact with a macro cell. The RAN configuration refers to a heterogeneous cell configuration or a hierarchical cell configuration in which small cells for low power/near field communication coexist in addition to an existing macro cell-based homogeneous network. An object of a new RAN configuration is to increase QoE (Quality of Experience) by providing a high data transfer rate to an end user.
In a complicated urban environment, it is inefficient to install an additional macro cell base station as in conventional cases. This is because system throughput is not significantly improved compared to increase of cost and complexity for installation of an additional macro cell due to a shadow area of the communication environment. Thereby, in a new heterogeneous cell structure, multiple small cells coexist in a macro cell, and are assigned resources according to a cell coordination scheme to serve UEs. Such heterogeneous cell structure is intended to provide a high data transmission rate for end users to enhance Quality of Experience (QoE).
In small cell enhancements for E-UTRA and E-UTRAN study item (SI) as one of 3rd generation partnership project (3GPP) standard scopes, research has been ongoing into enhancement of indoor/outdoor scenarios using low power nodes, and the scenarios is described in 3GPP TR 36.932. In small cell enhancements for E-UTRA and E-UTRAN SI, research has been conducted to draw advantages of concept of dual connectivity to small cell layers and a macro cell layer in which a user uses the same or different carriers.